ref: d555dfdc696e377a96fb5e1923d19f5175464a6d
dir: /vp9/encoder/vp9_picklpf.c/
/*
* Copyright (c) 2010 The WebM project authors. All Rights Reserved.
*
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
*/
#include <assert.h>
#include <limits.h>
#include "./vpx_scale_rtcd.h"
#include "vpx_mem/vpx_mem.h"
#include "vp9/common/vp9_loopfilter.h"
#include "vp9/common/vp9_onyxc_int.h"
#include "vp9/common/vp9_quant_common.h"
#include "vp9/encoder/vp9_encoder.h"
#include "vp9/encoder/vp9_picklpf.h"
#include "vp9/encoder/vp9_quantize.h"
static int get_max_filter_level(const VP9_COMP *cpi) {
if (cpi->oxcf.pass == 2) {
return cpi->twopass.section_intra_rating > 8 ? MAX_LOOP_FILTER * 3 / 4
: MAX_LOOP_FILTER;
} else {
return MAX_LOOP_FILTER;
}
}
static int try_filter_frame(const YV12_BUFFER_CONFIG *sd, VP9_COMP *const cpi,
int filt_level, int partial_frame) {
VP9_COMMON *const cm = &cpi->common;
int filt_err;
vp9_loop_filter_frame(cm->frame_to_show, cm, &cpi->mb.e_mbd, filt_level, 1,
partial_frame);
filt_err = vp9_get_y_sse(sd, cm->frame_to_show);
// Re-instate the unfiltered frame
vpx_yv12_copy_y(&cpi->last_frame_uf, cm->frame_to_show);
return filt_err;
}
static int search_filter_level(const YV12_BUFFER_CONFIG *sd, VP9_COMP *cpi,
int partial_frame) {
const VP9_COMMON *const cm = &cpi->common;
const struct loopfilter *const lf = &cm->lf;
const int min_filter_level = 0;
const int max_filter_level = get_max_filter_level(cpi);
int filt_direction = 0;
int best_err, filt_best;
// Start the search at the previous frame filter level unless it is now out of
// range.
int filt_mid = clamp(lf->filter_level, min_filter_level, max_filter_level);
int filter_step = filt_mid < 16 ? 4 : filt_mid / 4;
// Sum squared error at each filter level
int ss_err[MAX_LOOP_FILTER + 1];
// Set each entry to -1
vpx_memset(ss_err, 0xFF, sizeof(ss_err));
// Make a copy of the unfiltered / processed recon buffer
vpx_yv12_copy_y(cm->frame_to_show, &cpi->last_frame_uf);
best_err = try_filter_frame(sd, cpi, filt_mid, partial_frame);
filt_best = filt_mid;
ss_err[filt_mid] = best_err;
while (filter_step > 0) {
const int filt_high = MIN(filt_mid + filter_step, max_filter_level);
const int filt_low = MAX(filt_mid - filter_step, min_filter_level);
// Bias against raising loop filter in favor of lowering it.
int bias = (best_err >> (15 - (filt_mid / 8))) * filter_step;
if ((cpi->oxcf.pass == 2) && (cpi->twopass.section_intra_rating < 20))
bias = (bias * cpi->twopass.section_intra_rating) / 20;
// yx, bias less for large block size
if (cm->tx_mode != ONLY_4X4)
bias >>= 1;
if (filt_direction <= 0 && filt_low != filt_mid) {
// Get Low filter error score
if (ss_err[filt_low] < 0) {
ss_err[filt_low] = try_filter_frame(sd, cpi, filt_low, partial_frame);
}
// If value is close to the best so far then bias towards a lower loop
// filter value.
if ((ss_err[filt_low] - bias) < best_err) {
// Was it actually better than the previous best?
if (ss_err[filt_low] < best_err)
best_err = ss_err[filt_low];
filt_best = filt_low;
}
}
// Now look at filt_high
if (filt_direction >= 0 && filt_high != filt_mid) {
if (ss_err[filt_high] < 0) {
ss_err[filt_high] = try_filter_frame(sd, cpi, filt_high, partial_frame);
}
// Was it better than the previous best?
if (ss_err[filt_high] < (best_err - bias)) {
best_err = ss_err[filt_high];
filt_best = filt_high;
}
}
// Half the step distance if the best filter value was the same as last time
if (filt_best == filt_mid) {
filter_step /= 2;
filt_direction = 0;
} else {
filt_direction = (filt_best < filt_mid) ? -1 : 1;
filt_mid = filt_best;
}
}
return filt_best;
}
void vp9_pick_filter_level(const YV12_BUFFER_CONFIG *sd, VP9_COMP *cpi,
LPF_PICK_METHOD method) {
VP9_COMMON *const cm = &cpi->common;
struct loopfilter *const lf = &cm->lf;
lf->sharpness_level = cm->frame_type == KEY_FRAME ? 0
: cpi->oxcf.sharpness;
if (method == LPF_PICK_MINIMAL_LPF && lf->filter_level) {
lf->filter_level = 0;
} else if (method >= LPF_PICK_FROM_Q) {
const int min_filter_level = 0;
const int max_filter_level = get_max_filter_level(cpi);
const int q = vp9_ac_quant(cm->base_qindex, 0);
// These values were determined by linear fitting the result of the
// searched level, filt_guess = q * 0.316206 + 3.87252
int filt_guess = ROUND_POWER_OF_TWO(q * 20723 + 1015158, 18);
if (cm->frame_type == KEY_FRAME)
filt_guess -= 4;
lf->filter_level = clamp(filt_guess, min_filter_level, max_filter_level);
} else {
lf->filter_level = search_filter_level(sd, cpi,
method == LPF_PICK_FROM_SUBIMAGE);
}
}